Considerable development effort is currently being expended on the development of hydrogen and oxygen consuming fuel cells, and there is also interest in hydrogen burning engines. Such power systems require means for storage of hydrogen fuel which hold hydrogen in a safe form at ambient conditions and which are capable of quickly receiving and releasing hydrogen. In the case of automotive vehicles, fuel storage is required to be on-board the vehicle, and storage of hydrogen gas at high pressure is generally not acceptable for such applications.
These requirements have led to the study and development of solid-state compounds for temporary storage of hydrogen, often as hydrides. For example, sodium alanate, NaAlH4, can be heated to release hydrogen gas, and a mixture of lithium amide, LiNH2, and lithium hydride, LiH, can be heated and reacted with the same effect. Despite such progress, however, no known solid-state system currently satisfies targets for on-board vehicular hydrogen storage.
U.S. patent application Ser. No. 11/386,409, titled “XLi3N2 Compounds and Their Hydrides as Hydrogen Storage Materials,” by the inventor of this invention and assigned to the assignee of this invention, describes and claims a family of new compounds, XLi3N2, which form hydrides, XLi3N2Hn, where X is a 3d transition metal. This invention extends that family to certain additional XLi3N2 and XLi3N2Hn compounds for hydrogen storage.